A pressure vessel is used as a housing, and the like, for a compressor, such as an air conditioner, which is carried by an automobile, for instance, and has been required to reduce the weight recently. Accordingly, for housings of compressors in which pressure resistance is said to be required, light metals, such as aluminum and magnesium, whose densities are small, have been employed.
However, in a simple light-metal cast product, it is difficult to obtain the strength which is required for housings of compressors (the tensile strength is 200 MPa approximately in aluminum cast products), and the strength under high-temperature environment degrades further (it degrades by 30% or more of that at ordinary temperature in a high-temperature region of 200° C. or more in aluminum cast products). Therefore, in order to obtain a strength to such an extent that satisfies the required pressure resistance, thickening becomes necessary, however, there is a problem that the larger the thickness becomes the more likely it is that cast cavities occur.
In a cylinder block, a constituent member for a housing, a cast-iron liner has been press-fitted into a block body, and so on, which is made of light metal, in order to improve the rigidity of sliding portions and sliding characteristics, such as wear resistance, in order to improve the strength of compressor's housing without being accompanied by thickening. For example, in Japanese Unexamined Patent Publication (KOKAI) No. 59-074,353, an aluminum liner, which is formed by means of drawing process, is cast-wrapped in a cylinder bore, and a flame-sprayed layer is formed on the inner peripheral surface of the liner. Meanwhile, from the viewpoint of the issue of the adhesiveness between block body and cast-iron liner, a liner-less cylinder block, from which a cast-iron liner is abbreviated, has been developed. However, in the liner-less structure, since the rigidity of the sliding surface is low, it might be deformed depending on the extent of heat or internal pressure.
Moreover, in Japanese Unexamined Patent Publication (KOKAI) No. 10-318,038, a silicon-enriched layer, in which primary-crystal silicon is agglomerated, is formed on the inner wall surface of a cylinder bore, using a filtering material which comprises a fine wire material.